Abstract: This invention includes a heat exchanger that can be operated with a combustion turbine. This heat exchanger can be operated in either a simple cycle mode of operation or a combined cycle mode of operation. Preferably, the heat exchanger has a first heat transfer stage, a second heat transfer stage, a bypass stack and a damper. The damper and the bypass stack are preferably disposed between the first and the second heat transfer stages. Hot fluid can be received into the heat exchanger from the combustion turbine and directed through the heat transfer stages where heat is transferred from the hot fluid to the cooling medium flowing through the tubes of the heat transfer stages. Preferably, the hot fluid enters the heat exchanger upstream of the first heat transfer stage. After flowing through the first heat transfer stage, the hot fluid can be directed by the damper to either the bypass stack or the second heat transfer stage.

Abstract: A gas turbine system in which substantially all of the compressed air from the compressor portion of the gas turbine is used to fluidize a bed of solid fuel, such as char, in a pressurized fluidized bed gasifier so as to produce a hot gas. The hot gas flows through a heat recovery steam generator so as to produce steam, which is expanded in a steam turbine so as to produce shaft power. A first portion of the hot gas from the heat recovery steam generator is expanded in the turbine section of the gas turbine so as to produce additional shaft power. A second portion of the hot gas from the heat recovery steam generator is then used to cool the turbine section of the gas turbine, after further cooling and filtering. Since none of the turbine cooling fluid is obtained by bleeding compressed air directly from the compressor, the mass flow of the hot gas flowing through the gasifier, and, therefore, the hot gas it produces is maximized, thereby maximizing steam generation in the heat recovery steam generator.